Measles, also known as Rubeola or morbilli, is a highly infectious illness caused by a virus - a viral infection caused by the rubeola virus.
Measles is an endemic disease; meaning it is continually present in a community and many people develop resistance. If measles enters an area where the people have never been exposed the result can be devastating.
A measles outbreak in 1592 in the island of Cuba killed approximately two-thirds of the native population who had previously survived smallpox. A couple of years later half the indigenous population of Honduras died.
Over the last 150 years, estimates place the total global measles death toll at 200 million people. One fifth of Hawaii's population died in the 1850s from measles.
Scientists have identified 21 different strains of the measles virus.
Contents of this article:
Symptoms of measles
Measles symptoms can often include a reddish-brown spotty rash.
Measles symptoms may include the following:
- Coryza - runny nose.
- Dry hacking cough.
- Conjunctivitis - swollen eyelids, inflamed eyes.
- Watery eyes.
- Photophobia - sensitivity to light.
- Fever - this may be mild to severe and can reach 105F (40.6C) for a number of days. Fever may drop, and then rise again when the rash appears.
- Koplik's spots - very small grayish-white spots with bluish-white centers in the mouth, insides of cheeks, and throat.
- Aches generally all over the body.
- Rash - 3 to 4 days after initial symptoms a reddish-brown spotty rash appears. The rash can last for over a week. It usually starts behind the ears and spreads all over the head and neck. After a couple of days it spreads to the rest of the body, including the legs. As the little spots grow many of them will join together.
Although the majority of childhood rashes are not measles, you should take your child to the doctor if:
- You suspect it could be measles.
- Symptoms do not improve, or get worse.
- The fever rises to above 38C (100F).
- When the symptoms have gone, but the fever hasn't.
What causes measles?
Measles is caused by infection with the rubeola virus, a paramyxovirus of the genus Morbillivirus. The virus lives in the mucus of the nose and throat of an infected child or adult. The infected person is contagious for four days before the rash appears, and continues so for about four to five days afterwards.
You can become infected through:
- Physical contact with an infected person.
- Being nearby infected people if they cough or sneeze.
- Touching a surface that has infected droplets of mucus (the virus remains active for two hours) and then putting your fingers into your mouth, rubbing your nose or eyes.
How does a measles infection develop in a person?
As soon as it enters the body the virus multiplies in the back of the throat, lungs and the lymphatic system. It later infects and replicates in the urinary tract, eyes, blood vessels and central nervous system.
Scientists at the Mayo Clinic say that replication in the airways is not required. They found that a virus replicating only in immune cells causes measles in monkeys.
Experts say it takes from 1 to 3 weeks for the virus to establish itself. However people show symptoms 9-11 days after infection.
A person who has had measles before does not become infected again; cases of re-infection are very rare. However, anyone who has never been infected and has not been vaccinated and breathes in infected droplets, or is in close physical contact with an infected person is likely to become ill. Approximately 90% of people who share a house with an infected person and have no immunity develop measles.
On the next page we look how measles is diagnosed, the available treatments for measles, how measles can be prevented and the drop in measles mortality over the decades.